1. Field of the invention
The present invention relates to a system, method and apparatus for shipment/storage of perishable products, such as fresh vegetables and fruit, fresh fish, etc. in a controlled atmosphere environment, and more particularly to a novel method in which the controlled atmosphere is provided throughout the shipment and/or storage of the product, and the apparatus associated therewith.
2. Background Art
It has long been known that temperature, humidity and the composition of the surrounding atmosphere can effect the useful life of food products. Products that have benefited greatly using controlled atmosphere storage and controlled atmosphere transport include fruits, vegetables, orchids and flowers, meats, poultry, fish, and also grains and seed, among many others.
For many decades perishable food products (e.g. fresh meat) had been shipped in a refrigerated environment. When these have been shipped by rail, specially constructed refrigerated freight cars would be supplied with a quantity of ice periodically along the route to maintain the desired low temperature. Later, mechanical refrigeration units were supplied for freight cars, over the road trucks, trailers, etc.
With regard to the atmospheric conditions affecting the shelf life of such food products, it has long been known that with the use of "controlled atmosphere" techniques, the shelf life of fresh post-harvest product can by extended by two, or three times or more in comparison with the conventional air storage techniques, when used as a supplement to good temperature and humidity protocols. Also, it has been a practice to have fruits and vegetables ripen to an optimum point prior to sale in a controlled atmosphere and then shipped using controlled or conventional atmospheric techniques. The term "modified atmosphere" refers to replacement of ambient air with a particular gas mix, and then sealing the container holding the mixture. No further controls are generally employed to maintain this particular gaseous mix.
The controlled atmosphere process in one where gas replacement of ambient air is accomplished in a similar manner to modified atmosphere. However, there is a mechanism to continually refresh the gas mix so that the levels don't fall out of proper proportions due to biochemical and enzymatic reactions between the gases and the product being housed. The continual modification is termed "controlled atmosphere".
The controlled atmosphere process usually involves reducing the oxygen level in the immediate environment to inhibit oxygen loving and putrefying bacteria as well as the chemical oxidation processes. Controlled atmosphere techniques are commonly used to store vegetables and fruits in warehouses over many months. Without controlled atmosphere techniques in such warehouses, the product would perish quickly and all consumption would be seasonal only.
Ambient air is generally about 0.3% CO.sub.2, 20% O.sub.2 and 78% N.sub.2 with remaining 1.7% comprised of many other gases. Generally, the gas environment used in controlled atmospheric techniques is composed of CO.sub.2, O.sub.2, and N.sub.2. The proportions (or partial pressures) for optimum storage periods differ depending on the product. For lettuce, it may be only 2% CO.sub.2, 3% O.sub.2 and 95% N.sub.2. For cantaloupe it may be 18% CO.sub.2, 5% O.sub.2 and 70% N.sub.2. For poultry it may be 95% CO.sub.2, 1% O.sub.2 and 4% N.sub.2 . For some fish it may be 85% CO.sub.2, 5% O.sub.2 and 10% N.sub.2.
However, when the food products are enclosed, the natural bacteriological and chemical processes that occur can alter the atmosphere around the enclosed products greatly. For fruits and vegetables the ripening process is very active, and to maintain the desired atmospheric conditions, some actively produced CO.sub.2 and ethylene must be constantly removed and regulated. For post-harvest meats, poultry and fish, there is less active emission of generated products, but the post-rigor breakdown of the protein and fats is hastened in the presence of high levels of O.sub.2. Too little O.sub.2, however, will provide a different set of concerns such as allowing the toxic anaerobic bacteria to potentially flourish. Thus, it is highly desirable to change the atmosphere for protein products due to bacteriological and chemical processes, and this can be accomplished by constant purging of the aged air, and replacement with new, properly proportioned gases.
Most packaging materials used in food manufacture such as corrugated cartons, sbs fiberboard, styrofoam and polyethylene bags have a porosity that enables the gradual exchange of gases. Therefore, product that has been prepared and packaged in a standard method and with standard materials is generally very amenable to the benefits of controlled atmosphere storage and shipping.
For these reasons, equipment has been developed to maintain a controlled atmosphere for such food products when these are being stored for extended periods of time, or when these are being shipped by boat. Thus, specialized ocean shipping containers have been developed.
Specialized ocean containers are boxes that measure approximately 40 feet long, 8 feet wide and 9 feet high. The containers are available uninsulated-insulated or insulated with refrigeration units. Some units are available that are half this size, or 20 feet long, 8 feet wide and 9 feet high. Some companies have altered insulated refrigerated containers to permit the infusion of alternative gaseous atmospheres, and displacement of an ambient air atmosphere. Additionally they have placed into the containers extra seals to prohibit rapid gas exchange with outside air or loss of the gas or mixture. Some of these altered, refrigerated containers are also altered to install a railing just inside the doors that accepts a plastic curtain which serves to provide an additional seal against gas exchange.
However, there is an expense in modifying the basic design to incorporate the controlled atmosphere system, and one effect of this is that obtaining such specialized containers in a routing system used by shipping companies is often a time consuming process and can cause significant delays to acquire such containers. Normally, these are not used in routes involving most ports world wide, but instead are cycled in routes that are centers for fruit and vegetable production. Further, the controlled atmosphere techniques are often used in conjunction with refrigeration of the containers. All ocean shipping containers that use refrigeration have periodic defrost cycles. The periodicity may be as often as four hours or can be every 24 hours. The defrost cycles raise the interior of the containers several degrees for several minutes. Even small temperature changes on products have deteriorating effects.
One specialized ocean shipping container is provided by Transfresh Corporation. This system provides a sealed container with gas ports. The required gas is injected into the container, and the container is then sealed. There are mechanical processes that remove undesired levels of some gases such as ethylene and carbon dioxide. The system is primarily passive and is not capable of maintaining high levels of CO.sub.2 for meat, poultry and fish products over time. It functions primarily as a modified atmosphere control system as will be described below. This container requires that a plastic curtain be fitted into specialized tracks at the entrance (the back door), and the curtain must be removed to ventilate the container for access of the product.
Another ocean shipping container is manufactured by C. A. Global Express L. L. C. Their shipping container contains the gas cylinders, nitrogen systems and dispensing systems. It dispenses controlled levels of gaseous atmosphere to product held in sealed (transfresh- type) containers.
As another example, Carrier Transicold Corporation manufactures refrigerating systems, and modifies ocean shipping containers to provide these in somewhat the same manner as Transfresh Corporation. A nitrogen making module is placed in the container which allows the purging of unwanted levels of CO.sub.2 buildup from product respiration. However, these containers do not measure levels of CO.sub.2 above 25% which is often required for meat, poultry, and fish products.
In addition to the considerations of shipping the product in a controlled atmosphere environment, quite often when the product reaches the end destination, it is necessary to store it, either for local distribution at a later time or for further shipment. Thus, to continue the controlled atmosphere process, this generally requires a sealed room with proper ventilation equipment, oxygen masks for the workers, monitoring equipment and alarm systems. Another alternative is for the receiving party to maintain the product in a modified ocean shipping container at the destination location.
Generally, as indicated above, these specialized containers are sealed at the back wall, and a plastic curtain is placed over the entrance. Usually, the procedure to remove and replace the curtain takes a minimum of 20 minutes. The container would need to be evacuated of the high CO.sub.2 gases before a person can enter, and the replacement of the controlled atmospheric gases afterwards would take some time and a considerable quantity of gas.
One alternative to using controlled atmosphere techniques for time consuming shipments is to use air freight service, and for some highly perishable products this is the only viable way to ship such products to or from remote locations. In many circumstances, however, there is no practical way to ship fresh product from the region because the air freight is too expensive or too limited. In Alaskan fishing ports, this condition is common. As an example, the largest fish port in the United States (Dutch Harbor, Ak.) has less than one percent of all products shipped fresh. The cost to fly the product to a distribution center such as Seattle is about 65 cents per pound versus about 12 cents per pounds by sea container. However, the time it takes to ship by sea (without controlled atmosphere techniques) causes the product to deteriorate too much for the market to accept, so freezing is required. Floral shipments from South America face similar problems and have the disadvantage of occupying a relatively large amount of space. When properly packaged, these require a substantial volume for little weight, and the cost of air freight for these flowers is very high.
Another method of controlling the atmosphere surrounding a perishable food product or the like is called "modified atmosphere packaging". This is done by packaging the product with the desired gaseous mixture within the package and then sealing the package. Recent developments have also included gas "scrubbers" that eliminate internal packaged quantities of CO.sub.2 and O.sub.2 and ethylene. These scrubbers help the product to maintain an optimum level of gas, but can only approximate it and are subject to the limits of the scrubbing devices.
A filling machine to accomplish the modified air packaging technique is manufactured by M-Tech Incorporated. This enables the user to place the product into a bag, draw a vacuum and fill the bag with the desired gas mixture, after which the bag is sealed. A similar system is provided by CVP Systems Incorporated.
Also, films have been developed to allow one way gas transmission, particularly CO.sub.2 emissions from fruit and vegetable packaging. Again, these films help maintain a desired atmosphere, but usually with great tolerance in the gas proportions.
A search of the patent literature has disclosed a number of patents. These are as follows:
U.S. Pat. No. 5,529,178 (Gorlich) shows a gas tight shipping container in which a piece of meat is packaged. The air is replaced with the desired low oxygen content gas mix so that spoilage is retarded. In column 5, line 16, it is stated that it may be desirable to withdraw the low oxygen from the container at the point of sale, since if this is not done, the package with the low oxygen environment will cause the meat to have a purplish color. Therefore, in the supermarket, the upper permeable film 66 may be pealed back to allow the ambient atmosphere to enter the package so that the meat will take on a reddish color. PA1 U.S. Pat. No. 5,501,525 (Cox et al) discloses a bag system for holding meat or other food products. In use, the bag is flushed of air, and a more preserving gas mix is pumped in. This container has an outer bag and an inner bag. This is described as "bone-guard" and has a puncture resistant inner bag for preventing bones and other sharp surfaces from penetrating the inner and outer bags. PA1 U.S. Pat. No. 5,481,852 (Mitchell) discloses what is called a "method and apparatus to promote gas exchange from a sealed receptacle". PA1 This patent is directed primarily toward a method of injecting the gas components into the bag in a particular manner and sequence to provide a sealed, packaged product with the desired atmosphere therein. PA1 U.S. Pat. No. 5,389,036 (Halley) shows a storage vessel for storing grain. There is a gas impermeable enclosure having a water-vapor-permeable membrane to allow the grain to breathe and dry, and to prevent condensation and mold growth With the reduced oxygen concentration, any insect or other pests present in the grain will begin to use up the available oxygen until substantial anaerobic conditions are obtained to exterminate any living animals or organisms in the grain. PA1 U.S. Pat. No. 5,261,532 (Fauci) shows a reusable plastic bag, and is directed toward a particular construction of the bag, particularly the vent tubes. PA1 U.S. Pat. No. 4,572,360 (Lischka et al) discloses what is called a "herb package", and deals with the perforations in the pouch, some of these projecting outwardly, and some inwardly to act as valves for circulation of water. PA1 U.S. Pat. No. 3,905,410 (Arato), shows a fluid shipping bag that is provided with a filling connection 2, and a vent 3. PA1 U.S. Pat. No. 3,432,087 (Costello), shows a seal placed over a weak spot on a bag so that under high pressure material can flow out. PA1 U.S. Pat. No. 3,371,985 (Wyka), shows a disinfecting system in which air flows from a mattress 4, through a container of chemical treatment material at 2, and is propelled back into the mattress 4. PA1 U.S. Pat. No. 3,209,674 (Payne), shows a vat for fermenting pickles and the like with a cover that is provided with an over pressure relief valve and an access tube that can be closed when not in use. PA1 U.S. Pat. No. 2,870,954 (Kulesza), shows a bag that is provided with a vacuum valve so that when the bag is exposed to a vacuum the air in it is withdrawn, and no new air can flow in. PA1 U.S. Pat. No. 2,638,263 (Jesnig), shows a bag with an integral check valve through which air can be withdrawn. PA1 U.S. Pat. No. 2,314,317 (Walter), shows a system in which dressed poultry is quick frozen. It is placed in a bag or wrapped and a pipe supplied with chilled air is placed in the cavity and a second tube that sucks out the air after it has chilled the poultry. In some embodiments there are several bags, each of which is provided with a cold air source, and suction pipe. PA1 U.S. Pat. No. 1,119,986 (Pleger et al), provides a garment container that is shown with several means for providing fumigant to the garment. There is a pocket 15, in which material may be placed, or a bulb 19, can be provided to inject a treating chemical. PA1 a) a first category of a quantity of product not reasonably requiring further controlled atmosphere environment; PA1 b) a second category of a quantity of product requiring continued presence in the controlled atmosphere environment.
The following patents disclose various features of possible interest.